Kristen Stewart and Rupert Sanders admit they had a tryst, but was it an onset romance that began while they were filming Snow White and the Huntsman?

Nope.

A source insists that the two didn't get together until long after they wrapped the movie and its international publicity tour.

"I can guarantee you 100 percent that nothing happened when they were working—nothing!" the source said.

K.Stew and Sanders were snapped by paparazzi kissing just last week in Los Angeles. Less than 24 hours after their involvement was revealed last night, both Stewart and Sanders released separate apologies.

No surprise, but Stewart is laying low right now with no plans to be out and about anytime soon.

"She knows she messed up big time," the source said. "There's no getting around that. She's not doing well, but what do you expect?"